About an hour into the print we started hearing a loud click from the back where the feeder is located and the PLA that came with the printer is either being flattened or the gear the pulls the PLA is grinding away at the PLA and it will not forward any material.
There's a few possible problems. For one thing you might just be printing too fast and/or too cold. Try 50mm/sec and 220C. In general stay at 1/2 the speed of the dark blue line here (it depends on layer thickness and temperature):
http://umforum.ultimaker.com/index.php?/topic/4127-um2-extrusion-rates-revisited/
The loud clicking sound at the back is the feeder missing steps. This is on purpose - by design. The idea is if the pressure gets too high in the head because you are printing too fast or cold then it's better to skip steps then to grind the filament. Unfortunately you have grinding *anyway*.
So again, 220C at 50mm should fix the skipping problem.
As far as your filament getting squished flat - this is possibly more serious. The glass temp of PLA is around 50C which is a comfortable hot tub temperature. I recommend just to "get a feel for it" that you take a few inches of filament and boil some water in the microwave then take the water out and dip the filament in the hot water (now probably at 80C) for about 10 or 20 seconds. Take the filament out and play with it - bend it - squish it. Until it hardens.
Now to the fix - this is a recent problem on some printers. One fix is to crank the AC. My bed and nozzle are at 20C room temp when I haven't used the printer in a few hours. What's your room temp? The other fix is to remove the back left metal cover that hides the 2 steppers back there. It is held in by only 2 screws - very easy to remove. Then use a table fan and place it in front of the UM2 aiming the air flow at the stepper. That can improve things greatly!
UM is working on other fixes but these 2 fixes work fine for even room temps at 90F (35C)!
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IRobertI 521
Print settings would be helpful to know.
Also, when you removed the failed bit, did you also clean the little knurled sleeve that bites into and moves the filament? A hardy blow and/or some scrubbing with a toothbrush should be enough to clean it. If it's clogged up with plastic it will not be able to grip the filament properly.
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